1. Field of the Invention
This invention relates to a method of and apparatus for use in field-forming bell and spigot joints in pipe, and more particularly to such method and apparatus for use in forming such a joint by inserting a pipe or spigot into a pipe bell or external gland wherein one of the assembled elements is out-of-round.
2. Description of the Prior Art
A push-on bell and spigot pipe joint is conventionally formed by initially installing an elastomeric sealing gasket in a recess within the bell of a first pipe, valve or fitting (hereinafter, pipe), then aligning the spigot end of a second pipe adjacent the open end of the bell and pulling or pushing the second pipe toward the first with a force sufficient to telescope the spigot into the bell through the resilient gasket. Typically, a lubricant is placed upon the external surface of the spigot end to facilitate the telescoping movement and to reduce the likelihood of damage to the elastomeric gasket material.
Mechanical or "stuffing box" joints typically involve assembling a gland onto the spigot and a sealing gasket is mounted on the projecting spigot end. The spigot is then inserted into the mechanical joint socket, or bell, with the gland lip compressing the gasket to form a seal as the gland and bell are bolted together. The term "bell and spigot joint" as used herein is, when appropriate, intended to include both mechanical and push-on bell and spigot joints.
In the manufacture of bell and spigot pipe from ductile iron, rigid plastic or composite material, either the spigot or both the bell and spigot of each length of pipe may be provided with a contoured generally conical surface to facilitate inserting the spigot of one pipe in the bell of another. The camming, or funneling surfaces cooperate during assembly of a joint to guide the spigot into the bell, thereby eliminating the necessity for precise alignment and to some extent also enabling a joint to be formed despite one or both of the pipe ends (typically the spigot end) being slightly out-of-round. The camming or funneling surfaces on both the bell and spigot ends of typical bell and spigot pipe is shown, for example, in U.S. Pat. No. 5,197,768, assigned to the assignee of the present invention. Glands employed for mechanical joints also employ camming surfaces which cooperate with the camming surfaces on the pipe spigot.
In the process of manufacturing bell and spigot pipe, both the bell and spigot ends of each pipe section are typically inspected and, if necessary, subjected to rounding procedures so that the finished pipe is substantially circular in cross section adjacent each end. Despite precautions taken during manufacture, however, the bell and/or spigot end may become slightly out-of-round in cross section. Due to the substantially heavier cross section and the resultant increase in strength and stiffness, the bell section of the as-manufactured pipe is less likely to be out-of-round than the lighter weight spigot end. As indicated above, however, typically the out-of-roundness of the as-manufactured pipe is not so severe that the camming or funneling surfaces will not be effective to cam the spigot into a configuration substantially complementary to the bell during assembly of the joint in the conventional manner without modifying the pipe. During insertion, the greater strength of the bell will result in it retaining essentially its original shape although some deformation, or rounding, of the bell may also occur. Since the deformation of the bell typically is small relative to that of the spigot, it will be assumed herein that only the spigot is rounded during assembly.
While the ends of manufactured pipe are generally round within acceptable limits, it is not uncommon for such pipe to be substantially out-of-round intermediate its ends. Also, it is frequently necessary to cut a length of pipe at a location intermediate its ends to form a joint at a particular location to install a valve, fitting or the like. Thus, it is not uncommon for the cut section to be out-of-round to the extent that the maximum radius of its outer surface substantially exceeds the mating inner surface radius of the to the bell to which the cut section is to be joined, in which case it is necessary to reshape, or "round" the cut end (hereinafter, spigot) before telescoping it into the bell. The rounding procedure must reduce the maximum radius of the spigot at least to the extent that the funneling surface on the spigot and/or bell can complete the rounding action during insertion into the bell.
It is common practice to internally "round" a severely out-of-round pipe end by initially determining the maximum and minimum diameters of the end to be rounded and to apply an expansive force along substantially the minimum diameter. Typically, this is accomplished by a jacking operation, employing a hydraulic or mechanical jack in the open pipe end, along with suitable blocks and resilient pads as required depending upon the diameter of the pipe. The jacking operation may be accompanied by impact loads applied, for example, by striking with a sledge, especially if localized distortion is involved. Frequently, it is necessary to repeat the expansion or jacking operation a number of times to round the pipe sufficiently to enable a joint to be formed. This diametrical jacking procedure requires substantial time and skill to be accomplished effectively and safely.
In an alternate procedure practiced in the past, an external clamping force is applied across the maximum diameter using a beam clamp in which a pair of beams are positioned on diametrically opposite sides of the pipe substantially tangent thereto at the maximum diameter. The beams are forced toward one another by manually turning nuts onto threaded rods extending through openings in the ends of the beams. Again, it may be necessary to repeat this clamping procedure until the pipe will sustain the necessary degree of roundness in those instances where work space does not permit the joint to be formed before the external clamp is removed from the pipe.
It is, therefore, a primary object of the present invention to provide an improved method of forming push-on or mechanical bell and spigot joints employing a bell, gland or spigot which is out-of-round, and to an improved rounding devices for use in forming such bell and spigot joints.
Another object is to provide such an improved method in which removable rounding devices are attached to a pipe bell or external gland, which devices present an extended funneling or camming surface to engage the spigot to round the spigot during insertion of the spigot.
Another object is to provide an improved rounding device which may readily and easily be detachably mounted onto a pipe bell before assembly of the joint, and which may be removed after forming of the joint for reuse.
Another object is to provide such rounding devices which may be employed with various pipe joint configurations and pipe materials and with pipe produced by various manufacturers.
Another object is to provide such a method and device which is particularly well suited for use for forming a bell and spigot joint using a field-cut pipe which is out-of-round.
Another object is to provide such rounding devices which may be left installed as a part of the finished bell and spigot joint to provide improved axial alignment between the joined bell and spigot and thereby improved joint offset performance.